On Fri, Oct 22, 2010 at 04:38:49PM +0200, Michael S. Tsirkin wrote:
> On Fri, Oct 22, 2010 at 01:35:47PM +0200, Markus Armbruster wrote:
> > "Michael S. Tsirkin" <m...@redhat.com> writes:
> >
> > > On Wed, Oct 20, 2010 at 05:18:56PM +0900, Isaku Yamahata wrote:
> > >> glue pcie_push_attention_button command.
> > >>
> > >> Signed-off-by: Isaku Yamahata <yamah...@valinux.co.jp>
> > >
> > > So as a high level command, I think we need to
> > > think about how to tie this into pci_add/pci_del.
> > > Right?
> > [...]
> >
> > Do we have consensus how our set of commands for hot plug should look
> > like? We talked about it, but did we reach consensus? If yes, did we
> > write it down somewhere?
>
> I think for simple things yes:
> - command to send hotplug notification to the guest
> - command to immediately add/remove the device
> - event to notify about guest ack
> - way to poll status: did guest ack last command?
I'm not sure about guest ack. Let me check my understanding.
The current qemu pci hot plug has its own hot plug controler,
PIIX4_PM, which relies on ACPI.
- command to add the device into the slot
This corresponds to physically inserting the device into the slot.
- qemu pci hot plug case: device_add/pci_add command.
The qemu pci hot plug controller, PIIX4_PM, detects the insertion,
then notify the guest OS of the event via ACPI, _L01.
The guest OS would start to probe the device.
- pci express native hot plug case: device_add/pci_add command.
The pcie hot plug controller detects the the insertion,
then notify the guest OS of the event via interrupt.
The guest OS would start to probe the device.
- command to remove the device from the slot
This corresponds to physically removing the device from the slot.
- qemu pci hot plug case: No corresponding command.
There is no way to remove the pci card forcibly from the slot.
- pci express native hot plug case: device_del/pci_del
After the removal of the card, the hot plug controller notifies
the guest OS via interrupt.
- command to send hotplug notification to the guest
command to push attention button.
This corresponds to pushing the button near the slot.
- qemu pci hot plug case: device_del/pci_del command
Maybe the button is called an eject button.
When the button is pushed, the hot plug controller notifies
the guest OS via ACPI, _L01.
Then, guest OS reacts the event by calling ACPI \_SB.PCI0.S<n>._EJ0
method. It program the hot plug controller to eject the device
in the given slot. As a result, the device is removed from the slot.
If the guest OS doesn't call _EJ0 (nor programs the controller directly),
the device stays there.
There is no way to remove the pci card without the guest OS
intervention.
- pci express native hot plug case:
pcie_push_attention_button command with my patch series.
The hot plug controller raise the interrupt to the guest OS.
There is no specified action from the OS.
- a way to get the slot status
new command for QMP/HMP? or enhance info pci?
- QMP event for qemu to notify the slot status change
e.g. when LED status is changed, qmp event will be sent.
> Existing ones will keep function:
> - send notification and when acked remove device
> - add device and send notification
> These are useful for human monitor but maybe not
> for management.
>
>
> --
> MST
>
--
yamahata
